1. Field of the Invention
Embodiments of the present invention relate to spectrophotometry of physiologic tissue, which may include quantitative measurement of reflection or transmission properties of a tissue as a function of wavelength. Specifically, embodiments of the present invention relate to using light emitting nanostructures (LEN), such as light emitting nanotubes, in spectrophotometry.
2. Description of the Related Art
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Spectrophotometry may include the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength. Spectrophotometry of living tissues includes pulse oximetry, which may include non-invasive techniques that facilitate monitoring of a patient's physiological characteristics (e.g., blood flow characteristics). For example, pulse oximetry may be used to measure blood oxygen saturation of hemoglobin in a patient's arterial blood and/or the patient's pulse rate. Specifically, these measurements may be acquired using a non-invasive sensor that passes light through a portion of a patient's blood perfused tissue and photo-electrically senses the absorption and scattering of light through the blood perfused tissue. A typical signal resulting from the sensed light may be translated into what is referred to as a plethysmographic waveform. Once acquired, this measurement of the absorbed and scattered light may be used with various algorithms to estimate an amount of blood constituent in the tissue. It should be noted that the amount of arterial blood in the tissue is time varying during a cardiac cycle, which is reflected in the plethysmographic waveform.
The accuracy of blood flow characteristic estimations obtained via pulse oximetry depends on a number of factors. For example, variations in light absorption characteristics can affect accuracy depending on where (e.g., finger, foot, or ear) the sensor is applied on a patient or depending on the physiology of the patient. Additionally, various types of noise and interference can create inaccuracies. For example, electrical noise, physiological noise, and other artifacts can contribute to inaccurate blood flow characteristic estimates. One source of inaccuracy in measurements obtained by traditional pulse oximeter sensors is inequality between optical pathways from emission to detection points for lights of different wavelengths. Indeed, light emitted from different points may not pass through the same portions of tissue. Such differences in optical pathways make traditional pulse oximeter sensors sensitive to physiological changes, geometrical changes and so forth.
Additionally, traditional pulse oximeter sensors can be inefficient. For example, traditional pulse oximeter sensors often use light emitting diodes (LEDs) that consume a significant amount of power and that produce undesirable heating effects. Indeed, when deep penetration of light into a patient's tissue is desirable to detect certain blood flow characteristics, for example, the increased intensity required of the LEDs may cause discomfort to the patient due to heating. Further, with respect to coupling a sensor to fiber optic cables, traditional pulse oximeter sensors may be inefficient because coupling fiber optics with larger and/or multiple spaced emitters (e.g., LEDs) results in inappropriate matching of fiber diameter and numerical aperture.
Accordingly, it is desirable to provide a system and method that efficiently and conveniently operates to provide accurate and consistent spectrophotometric measurements.